anime slashes and hard impact effects in blender 2.9 eevee
About the impact, using your already made object, I gave it the needed shader and got result.

It's described like this:
First, we get the Object Coordinates, sop we get the &quot;-1 to 1&quot; gradient. Then, using Separate XYZ we get the Z channel of the vector. Now, our Output is BW, going from -1 through 0 and then 1.  After this, we use a math node, performing action Absolute- this will ignore the sign before each number, so all negative values will become positive, while keeping the positive as is. Right now, we don't have a &quot;-1 through 0 to 1&quot; gradient, we have &quot;1 to 0 to 1&quot;- this will result a black line in the middle.
After this, we use Mix RGB nodes, set to &quot;Color Burn&quot; and &quot;Color Dodge&quot; to control the line. Mora Fac on the Color Burn will result a thicker line, and more Fac on the Color Dodge will result a harder falloff(harder edge between black and white).
Now, we use this thing as a mask for our Mix Shader. By putting Emission in the first socket, it will appear where the value is zero. The Transparent BSDF will appear on white values- this way the black line from our mask is now emission, and the rest is transparent. By adjusting the falloff between black and white, we can make the emission to blend with the transparency and so it will be faded on the edges.
So now you have it. But the problem is- how to move it?
That's fairly simple- we cant do it from the BW part, but because its all formed at the midpoint of the Object coordinates, we can move that mid point and thus move the line. So, we just add a Vector Math node before the BW part and we add some value on the axis we are using- in our case Z. Then, you can keyframe the Z axis value and boom, you have and animation,